_s/js/navigation.js

/**
 * navigation.js
 *
 * Handles toggling the navigation menu for small screens.
 */
( function() {
	var container, button, menu;

	container = document.getElementById( 'site-navigation' );
	if ( ! container ) {
		return;
	}

	button = container.getElementsByTagName( 'button' )[0];
	if ( 'undefined' === typeof button ) {
		return;
	}

	menu = container.getElementsByTagName( 'ul' )[0];

	// Hide menu toggle button if menu is empty and return early.
	if ( 'undefined' === typeof menu ) {
		button.style.display = 'none';
		return;
	}

	menu.setAttribute( 'aria-expanded', 'false' );

	if ( -1 === menu.className.indexOf( 'nav-menu' ) ) {
		menu.className += ' nav-menu';
	}

	button.onclick = function() {
		if ( -1 !== container.className.indexOf( 'toggled' ) ) {
			container.className = container.className.replace( ' toggled', '' );
			button.setAttribute( 'aria-expanded', 'false' );
			menu.setAttribute( 'aria-expanded', 'false' );
		} else {
			container.className += ' toggled';
			button.setAttribute( 'aria-expanded', 'true' );
			menu.setAttribute( 'aria-expanded', 'true' );
		}
	};
	
	// Fix child menus for touch devices.
	function fixMenuTouchTaps( container ) {
		var touchStartFn,
		    parentLink = container.querySelectorAll( '.menu-item-has-children > a, .page_item_has_children > a' );

		if ( 'ontouchstart' in window ) {
			touchStartFn = function( e ) {
				var menuItem = this.parentNode;

				if ( ! menuItem.classList.contains( 'focus' ) ) {
					e.preventDefault();
					for( var i = 0; i < menuItem.parentNode.children.length; ++i ) {
						if ( menuItem === menuItem.parentNode.children[i] ) {
							continue;
						}
						menuItem.parentNode.children[i].classList.remove( 'focus' );
					}
					menuItem.classList.add( 'focus' );
				} else {
					menuItem.classList.remove( 'focus' );
				}
			};

			for ( var i = 0; i < parentLink.length; ++i ) {
				parentLink[i].addEventListener( 'touchstart', touchStartFn, false )
			}
		}
	}

	fixMenuTouchTaps( container );
} )();